<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script src="https://cdn.jsdelivr.net/npm/vue@2.6.10/dist/vue.js"></script>
</head>

<body>
    <div id="app">
        <h1>全名:{{fullName}}</h1>
    </div>
    <script>
        Vue.config.productionTip = false;
        
        const vm = new Vue({
            el: "#app",
            data() {
                return {
                    firstName: "wang",
                    lastName: "zhongwang",
                    fullName: "",
                }
            },
            /* 使用watch获取全名 */
            watch: {
                firstName:{
                    immediate: true,//立即监听
                    handler() {
                        this.fullName = this.firstName + " " + this.lastName;
                    }
                },
                lastName:{
                    immediate: true,//立即监听
                    handler() {
                        this.fullName = this.firstName + " " + this.lastName;
                    }
                }
            }
        })
</script>
</body>

</html>